Cases are known which have a cavity that constitutes the housing for a heat exchanger, and into which the heat exchanger is inserted by sliding drawer-like to be fixed therein by any suitable means. The case includes at least one conduit that opens into the cavity to admit air to be heated by passing through the heat exchanger's nest of tubes and then distributed around the passenger space. Sealing strips are applied to the heat exchanger around its end to avoid air leaking out from the open end of the cavity through which it was inserted therein. Sealing strips are similarly applied to either side of the heat exchanger's nest of tubes inside the cavity, particularly in between the smaller longitudinal walls of the heat exchanger and the longitudinal walls of the cavity, in order to prevent the air circulating in said conduit from passing around the nest of tubes rather than through it.
Preferred embodiments of the present invention simplify the assembly of a heat exchanger in such a case, and thereby reduce its cost.